C9 missing

[Ken Sair]

I am experience an engine missing under certain conditions and am looking for ideas. 18 months ago I had a fuel injector on my C9 replaced. The symptoms were coach shudder under trhe slightest acceleration. Turned out the #4 cylinder fuel injector failed.

Then in march 2009 we were coming out of the Sierra Madre mountains in Mexico and used the exhaust brake exstensively for many miles. Upon reaching the bottom, and accelerating, I experienced the same MH shudder as when the fuel injector failed. Any attempt at acceleration caused the whole coach to shake. Again, it felt as if it was running on 5 cylinders. About 15 minutes later (with light acceleration) the symptoms disappeared.

Fast forward to last week (11 months later). We were coming into San Diego on I-8. There is a long stretch of over 13 miles with 6% plus grades. I used the exhaust brake extensively and all worked well. Again, at the bottom I accelerated and the coach began to shudder again. It had not done so for the past 11 months. Anyway, I limped it along for a few miles till I arrived at my destination and turned it off. 45 minutes later, we went to leave and all was well. We parked for a week and left today heading to Temecula. About the 10th hill (again, using the exhaust brake on the downhills) I accelerated and damned if it didn't shudder upon acceleration. Same symptoms, like it was running on 5 cylinders. I limped it to the next offramp and called CAT hotline who put me in touch with a Freightliner business in Fortuna CA. After a brief rehash he felt it was the fuel pump failing. he could not explain why it kinda fixed itself after setting for a half hour. Anyway, I was on hold with parts for over 30 minutes. Got fed up and decided to head to the campground. After 45 minutes the coach started and ran just fine.

Its done this twice in the last week. It then 'repaired itself' after setting for 30-45 minutes. The symptoms are identical to when the fuel injector faild 18 months ago. I am getting no engine lights etc. All temps and guages are normal. I checked the filters and no water was found. The problem is occuring after long extended use of the exhaust brake but goes away after a brief rest period.

If anyone has ideas, I'm listening. I will be taking it to CAT and check for computer codes. Just like to go in educated.

tx, Ken

[Daryl Beck]

Could it be that the exhaust brake is not opening fully and causing the miss you are describing?  

[Ken Sair]

The exhaust brake works fine. Turns off and on like always. Its after I turn if off after a long downhill and accelerate that the engine misses.

[Edward Buker]

It seem like your problem is repeatable enough that you should be able to make it happen. I would consider getting hold of an IR gun and see if you can get a reading on each port of the exhaust manifold from the rear hatch. You could try this measurement with your engine at idle to get the technique down, then hot and operating normally. If you get the problem to reoccur you can then measure and see if one port is significantly lower in temp. That would most likely indicate an injector problem with one cylinder. Your symptoms are repeatable enough that someone at Cat should have seen this and have a definitive answer. I would be inclined to go to one of the largest Cat truck dealerships near you. They would have far more insight than most Freightliner dealers. If you are interested in trying the IR gun there are some at this site. One that has a decent high temp range up to 932F for $67 which seems reasonable. I have been told that a symptom of a failing pump is surging at idle and low RPM range. I'm sure there are other symptoms that I am unaware of. Wagner Cat truck dealership in Denver has an excellent trouble shooting team from my experience. Might be worth a call. Hope this helps.
http://www.arizonatools.com/tools/temperature-guns-and-probes/?gclid=CJXU6tephaACFRy4sgodRCO9mQ

[Gerald Farris]

Ken,
From the symptoms that you described, it sounds like a fuel delivery related problem to me, but that is just a guess. I would say that the highest probably would be an injector, followed closely by a pump problem.

The Caterpillar repair shop should be able to tell what the problem is by reviewing the ECM (Engine Control Module) history if any fail codes were set. The down side is, if there are no codes set in the ECM  they might have to duplicate the problem to fix it.

A restricted fuel filter can cause an engine miss, but I assume that you have changed it, especially if you were in Mexico when the problem started.

Gerald  

[Richard And Babs Ames]

We have replaced two injectors on our MH in 100,000 plus miles. First set a code (check engine light) and the second did not but it showed up whe they hooked up the computer.

 The  CAT RV help line
 http://catrvclub.org/cat_rv_contacts.htm
is a great resource to see if there are any service advisories in reference to your problem. Be sure to have your engine SN and Build when you call them.

[Ken Sair]

Thanks all. I have not changed fuel filters yet, since it happened only twice in one year. The thing thats got my brain working overtime is the problem 'fixes' itself after its shut down for 30-45 minutes. And, each of the 3 times its happened its been immediately after long use of the exhaust brake, which to me doesn't relate to fuel delivery. And, the symptoms are identical to the ones that existed when a previous fuel pump failed. My brain is hung up on it occuring after exhaust brake usage. Except for these 3 instances it has been performing flawlessly.

Guess I'll run it into the shop. Called the CAT hotline and the nearest facility that handles C9's is the Freightliner dealer in Fortuna CA. Even thats 50 miles away.

[Joel Ashley]

Like Daryl, I'm still suspicious of the exhaust brake, though you said you thought it was OK, and whether it's operating properly when things are hot and its valve is supposed to be fully open.  

[Edward Buker]

I think you indicated that the last time you had the problem it was an injector and not the fuel pump that failed. You mentioned the fuel pump failing in your last post which is a bit confusing.

If it was the exhaust brake not fully opening I do not think it would create a shudder. My guess is that the shudder comes from going through a compression stroke without any fuel to fire which puts things out of balance. If all cylinders were firing and the exhaust brake was partially shut then I think things would be in balance but you would lack power.

These injectors and pumps have very tight tolerances to meter the fuel precisely in order to meet emission standards. It is concievable that you build higher temperatures in the injector while using the exhaust brake, especially after the heavy load and heat of climbing and it siezes the injector when the tolerances are reduced due to expansion. When your engine returns to lower temperature the expansion reduces and it starts to work again. To some extent the injector is cooled by fuel usage which you stop while running the exhaust brake. If this mechanism was taking place in the pump i think it would affect all the cylinders and provide another symptom. This is one possible explanation, Cat will have the real answer.

I mentioned in my last post on this subject that having a Cat sign on a Freightliner dealership does not make them experts. I was towed into a Freightliner dealer with a Cat sign near Denver. Two days later I called up the largest Cat dealership I could find in Denver and had my coach towed there. They had it fixed in 6 hours and the knowledge base there was worlds apart from the Freightliner dealership. If this is not a common issue you may want to discuss your problem with a major Cat dealership and see what they think.

[Ken Sair]

Thanks all. The exhaust brake is working properly. Turns on/off as usual and is slowing the coach the same as when brand new. I have not had a fuel pump issue to date to my knowledge. The 'missing' is occuring after long downhill runs using the exhaust brake and then normal acceleration on the flat land or up the next incline.

Like I said, the symptoms are exactly the same as when I lost a fuel injector in Oct 2008. They are, engine missing like running on 5 cylinders instead of six. More throttle pressure increases the coach 'shudder'.

What has me baffled is that twice last week when it happened, I shut off the motor for 30-45 minutes and then on re-start the engine ran perfect. My opinion as the operator is that sometime during the extended use of the exhaust brake on long downhill runs , the fuel injector will stick open/closed (whichever applies), thus causing it to operate on 5 cylinders which causes the coach 'shudder'. Then after a small 'timeout', it resets (for lack of a better term) and works properly.

Go figure. Hopefully I drove it long enough for an engine code to show up. Calling tomorrow for a Wednesday appointment.

So, I called CAT hotline again and spoke with Mark. he recommended a CAT dealer in Riverside CA which is only 27 miles away. He wouldn't venture a guess but I'm leaning towards the injector. Thats after a long phone conversation with Gerald this am.

[Richard And Babs Ames]

Something I just thought of is our first injector failure only occured when the engine was under load and hot. The injector would function properly when cold and not under load.

 Our engine a 3126B cools when using the exhaust brake so I did not mention it earlier.

[Ken Sair]

Update. Took the ol' girl to Johnson CAT in Riverside today. Explained situation and they had at it. Cylinders all check OK so its not a fuel injector. They performed an exhaust brake test and that was Ok also. Then checked the exhaust pipe outlet and all was OK. They were unable to duplicate the missing I experienced after extended downhill runs with the exhaust brake on. We discussed fuel pumps/fuel filters/cold starting etc. Very helpful folks.

They did venture an opinion though inspite of only 3 occurences in 11 months. Johnson CAT believes that extended downhill (one was 13 miles of 6% grade) exhaust braking was causing the brake to heat up and thus expand, if only a tiny amount. Then at the bottom, when throttle was necessary the brake would 'stick' partially closed. Then when I shut it down for 30-45 minutes it had time to cool down thus 'shrinking' to normal size and operated properly. It did work on the way to the shop but exhaust braking was limited to offramps etc. Being unable to duplicate the problem, I said thanks, handed over my $250 (they cut me some slack as they had it a little over 4 hours) and returned to the campground poorer but not much wiser. I did get the most recent CAT flash update for no charge. Tech said he felt guilty charging me for the computer running while he was checking other stuff. It had to do with fuel management of something.

So, tomorrow I call Jakebrake and pick their brains.

[Ken Sair]

Spoke with Jakebrake today. They dont believe the brake assembly itself is the issue. We all are convinced it is not an engine issue. They also didn't buy the metal expanding after extended use as things actually cool down because the engine fan engages with brake usage.

Jakebrake feels it could be one of two things, the solenoid itself (which can be activated electronically at   the shop and help closed for 15 min) or the air cylinder itself (air on-spring off). Need to take it back to CAT. Crap. Wished I'd have known this wednesday as I could have had themk cover all this under the 5 year warranty. They also asked if the 3 episodes occured after switch disengagement or throttle disengagement. I had no clue. I'll pay more attention. If it turns out the be warranted i'll address the $250 from last Wednesday then.

Anyway, I'll continue to monitor until late April when I take it to Holt CAT in San Antonio for the lash valve adjustment. I'll have them check then. Problem is not many long hills between here and there to duplicate problem.

Any, thats what I know.

[Bruce Benson]

Assuming you are coming east on I-10.  Take 70 east out of Las Cruces, enjoy a day at White Sands; take 82 east out of Alamogordo, enjoy a cool night in the pines of Cloudcroft; take 285 south at Artesia, enjoy a day at Carlsbad Caverns; join back up with I-10 at Fort Stockton.

You will add 2 nice long grades, 90 miles to your trip, avoid El Paso and enjoy some great natural wonders!

[Jerry Pattison]

Geez, can I relate to this!  I have a 98 Marquis with a C-12.  My experience was similar but different.  I had some instances of the engine "missing".  I thought at the time, how can a diesel engine miss?  Anyway, it got worse, so I called Cat, went to Cat service, they thought it was maybe engine mounts making the engine seem like it was missing, etc.  I discovered that it was missing more on right-hand turns (as up a highway).  Went on for months!

To shorten the story, it turned out to be a fuel temperature sensor that was intermittently shorting out the 5 volt supply to all those engine sensors.  So, for just milleseconds at a time, the engine sensors shut down, then came back on.  But, in my case, only in right turns.

Seems that the way that the cabling was tied together led to stress on the wire in right turns, leading further to a shorting of the 5 volt wire at the fuel temp sensor.

It took months of search, and only once I was able to get a service supervisor to ride with me and have the failure while he was in the coach could we prove to him that there was really a problem.  Fortunately, during this ride it failed and continued to do so while we pulled into the service bay, left the engine running, in gear,  while the computer was attached, and the analysis found it.

So, my message is, it is likely a simple solution, mighty hard to find, though!  Cut all those tight cable ties around the engine sensors!  Chuckle!!  And mention this forum to the service guy!

Good luck!